1. Field of the Invention
The present invention relates to an optical film, a polarizing plate, and a method for producing the optical film.
2. Description of the Related Art
An optical film having a function as a phase difference plate has frequently been used in a liquid crystal display apparatus, and for example, a λ/4 phase difference plate in a form in combination with a linearly polarizing plate has often been used as a circularly polarizing plate. In order to attain a high contrast in the inclination direction of a liquid crystal display apparatus in an IPS mode or like, various configurations using a combination of a positive A-plate with a positive C-plate as a phase difference plate have been proposed (for example, JP4592005B and JP2012-255926A).
On the other hand, WO2005/050269A proposes a phase difference plate having a reverse wavelength dispersion. A phase difference plate is usually difficult to be prepared as a phase difference plate giving the same effects as the light at any wavelength with respect to white light with a synthetic wave having mixed rays in a visible light region, and thus, for example, the phase difference plate functions as a ¼ wavelength plate with respect to light at a wavelength of 550 nm, but the phase difference plate does not function as a ¼ wavelength plate with respect to light at a wavelength of 450 nm or 650 nm, which causes problems such as coloration at the time of use.
To solve these problems, WO2005/050269A proposes a phase difference plate having reverse wavelength dispersion as a phase difference plate functioning in a broad wavelength region (broadband phase difference plate). Further, for example, a configuration in which two layers such as a λ/2 wavelength plate and a λ/4 wavelength plate are laminated by shifting a slow axis to be allowed to function as a broadband phase difference plate is also proposed (JP2004-238431A)